The present invention relates to processing liquid delivery systems for processing chambers, and more specifically to the removal of processing liquid from a processing liquid path of a processing liquid delivery system.
Many semiconductor processes such as chemical vapor deposition (CVD) employ vaporized processing liquids. These vaporized processing liquids are generated and supplied to a processing chamber via a processing liquid delivery system comprising an interconnection of pipes, valves, flow regulators and vaporizing mechanisms. Typically a separate vaporizing mechanism is provided for vaporizing each processing liquid, and is coupled to a source of processing liquid and a source of carrier gas. Although a number of vaporizing mechanisms exist (e.g., bubblers, injection valves, etc.), most conventional processing liquid delivery systems employ a plurality of injection valves for vaporizing processing liquids to be delivered to a processing chamber.
A typical injection valve comprises a processing liquid inlet for receiving a pressurized processing liquid, a carrier gas inlet for receiving a pressurized inert carrier gas, and an outlet for delivering a vaporized processing liquid/carrier gas mixture. The injection valve is heated such that when the processing liquid is injected into the carrier gas, the heat and the low partial vapor pressure of the processing liquid in the carrier gas cause the processing liquid to vaporize.
Over time injection valves can fail (e.g., due to mechanical failure) or clog (e.g., due to deposit formation within the injection valve from the interaction of processing liquid with other processing chemicals or with the injection valve itself) and must be replaced. However, the process of injection valve replacement is complicated when the processing liquid vaporized by the injection valve reacts deleteriously with air (e.g., moisture, oxygen, etc.) to form by-products (e.g., solid films such as oxides) that can damage the processing liquid delivery system or the processing chamber, contaminate subsequently processed semiconductor wafers or harm humans or the environment (e.g., toxic).
To prevent deleterious processing liquid formation during injection valve replacement, if possible, processing liquid is purged from all processing liquid paths exposed to atmosphere when the injection valve is removed. The processing liquid purging process, however, is difficult within conventional processing liquid delivery systems when processing liquids with strong adhesive properties such as metal-organics (e.g., tetrakis(dimethylamino)titanium (TDMAT)) must be purged from processing liquid paths, as described with reference to FIG. 1.
FIG. 1 is a schematic view of a conventional processing liquid delivery system 11 (xe2x80x9cconventional system 11xe2x80x9d) for delivering vaporized processing liquid to a processing chamber (not shown). The conventional system 11 comprises a source of processing liquid 13 operatively coupled (i.e., coupled either directly or indirectly so as to operate) to an injection valve 15 via a processing liquid path 17. Note that the processing liquid path 17 is shown broken to indicate that the source of processing liquid 13 may be a substantial distance (e.g., up to about 1-15 feet) from the injection valve 15.
Disposed along and forming a part of the processing liquid path 17 are a first isolation valve 19, a second isolation valve 21, a liquid flow meter 23 and a third isolation valve 25. The first isolation valve 19 is positioned near the source of processing liquid 13, the third isolation valve 25 is positioned near the injection valve 15, the liquid flow meter 23 is positioned near the third isolation valve 25 and the second isolation valve 21 is positioned near the liquid flow meter 23 as shown. A large number of other isolation valves typically are present along the processing liquid path 17 but are omitted for clarity.
The conventional system 11 also comprises a source of purging gas 27 (e.g., nitrogen, argon, or some other gas which does not react with the processing liquid) operatively coupled to the processing liquid path 17 via a purging gas line 29, and a pump 31 (e.g., a mechanical vacuum pump) operatively coupled to the processing liquid path 17 via a pump line 33. Disposed along and forming a part of the purging gas line 29 is a purge valve 35, and disposed along and forming a part of the pump line 33 is a pump valve 37.
During normal operation of the conventional system 11, the first isolation valve 19, the second isolation valve 21 and the third isolation valve 25 are open to allow processing liquid to flow from the source of processing liquid 13 to the injection valve 15 at a rate controlled by the liquid flow meter 23. The purge valve 35 and the pump valve 37 are closed to prevent processing liquid from being purged by the source of purging gas 27 and from being pumped by the pump 31.
If the injection valve 15 subsequently becomes damaged, defective, clogged or otherwise unusable (i.e., dysfunctional) and must be replaced, the injection valve 15 is isolated from the source of processing liquid 13 by closing the first isolation valve 19. Assuming the processing liquid is a metal-organic substance such as TDMAT or (Trimethylvinylsilyl)hexafluoro-acetylacetonato Copper 1 (CupraSelect(copyright)), the injection valve 15 cannot be directly disconnected from the conventional system 11 without posing a substantial health risk to the technician removing the injection valve 15 and without posing a substantial damage risk to the conventional system 11. TDMAT, for instance, reacts with moisture in the air to form by-products that are harmful to humans (e.g., amines) and solid films (e.g., oxides) that will contaminate the entire conventional system 11. Processing liquid, therefore, must be purged from the processing liquid path 17 prior to removing the injection valve 15.
To purge processing liquid from the processing liquid path 17, with the first isolation valve 19 closed and the second isolation valve 21 and the third isolation valve 25 open, the purge valve 35 and the pump valve 37 are opened. Purging gas thereby flows from the source of purging gas 27, through the purging gas line 29, through the processing liquid path 17 and through the pump line 33 to the pump 31. The purging gas dislodges absorbed processing liquid molecules from the surfaces of the processing liquid path 17, and the dislodged particles are pumped from the processing liquid path 17 via the pump 31. Pump/purge cycles (wherein the purge valve 35 is closed for a time period while the pump 31 continues to pump processing liquid and purging gas from the processing liquid path 17, followed by a time period wherein the purge valve 35 is opened so as to introduce more purging gas to the processing liquid path 17) may be performed to aid in processing liquid removal from the processing liquid path 17.
For processing liquids having strong adhesive properties (e.g., metal-organics), the pump/purge process described above is largely ineffective at removing processing liquid from the processing liquid path 17 to a level sufficient to prevent deleterious by-product formation when the injection valve 15 is removed from the conventional system 11. This is particularly true for TDMAT.
One approach to improving the purging effectiveness of the conventional system 11 is to employ a xe2x80x9cflushing liquidxe2x80x9d during purging that reduces the adhesive properties of the processing liquid. For instance, hexane may be employed to improve the purging of TDMAT from a processing liquid path.
Flushing liquids, however, typically are expensive and often possess undesirable properties. Hexane, for example, is flammable and requires special handling procedures that increase the operating costs of processing liquid delivery systems employing hexane-assisted purging.
Accordingly, a need exists for a processing liquid purging method and apparatus that more effectively purges a processing liquid from a processing liquid delivery system without requiring the additional expense and/or safety considerations associated with the use of flushing liquids.
To address the needs of the prior art, a novel valve arrangement is provided that allows for more effective purging of processing liquid from a processing liquid delivery system. Specifically, with the novel valve arrangement only a small portion of a processing liquid path must be purged of processing liquid to affect replacement of a dysfunctional injection valve. The small portion of the processing liquid path that is purged has a small surface area or xe2x80x9cwetting perimeterxe2x80x9d that may be effectively purged of processing liquid without the use of a flushing liquid.
The novel valve arrangement comprises a first isolation valve disposed near the liquid flow meter of the processing liquid delivery system, a second isolation valve disposed between the source of processing liquid and the first isolation valve, a purge valve disposed between the first and the second isolation valves and a pump valve disposed between the purge valve and the second isolation valve. Preferably each valve is configured to reduce the wetting perimeter of the processing liquid volume defined by the four valves (i.e., the isolated volume). For example, the wetting perimeter of the isolated volume may be reduced by employing valves having either a small wetting perimeter input or output port and by facing the small wetting perimeter port of each valve toward the isolated volume. Preferably there are no tees or other regions within the isolated volume which can not be directly purged with purging gas (i.e., dead legs).
With the novel valve arrangement, a processing liquid delivery system is formed in which a dysfunctional injection valve may be replaced without causing a health risk to humans or a damage risk to the processing liquid delivery system. To replace a dysfunctional injection valve, the first and the second isolation valves are closed and the pump and the purge valves are opened so as to purge processing liquid from the isolated portion of the processing liquid path between the first and the second isolation valves. Pump/purge cycles preferably are employed, and the purging process may be performed manually or automatically via a programmed controller.
Because of the small wetting perimeter of the isolated volume, and the lack of dead legs therein, the isolated portion of the processing liquid path is sufficiently purged of processing liquid to prevent deleterious by-product formation when the isolated portion is exposed to air (i.e., sufficiently purged), even when the purged processing liquid comprises a strongly adhesive metal-organic such as TDMAT. With the isolated portion of the processing liquid path effectively purged, the pump and the purge valves are closed and the first isolation valve, the liquid flow meter and the dysfunctional injection valve are removed as a sealed unit, and no processing liquid is released from either the processing liquid path or the sealed unit. A new (i.e., brand new, different, refurbished or cleaned) first isolation valve, liquid flow meter and injection valve then are connected to the processing liquid delivery system, preferably as a sealed unit, free of moisture or other species that may react with the processing liquid. The new isolated volume formed by the four valves is purged of moisture and other reactive species prior to reintroducing processing liquid thereto, in order to avoid contamination of the processing liquid delivery system. In this manner, processing liquid purging and injection valve replacement are performed more economically and with less health and equipment damage risk. The inventive valve arrangement also may be used to similarly affect replacement of other components within a processing liquid delivery system (e.g., a liquid flow meter, a processing liquid source, a gas source, a pump, a functioning injection valve, etc.).
Other objects, features and advantages of the present invention will become more fully apparent from the following detailed description of the preferred embodiments, the appended claims and the accompanying drawings.